Construction of Graphene‐Based “In‐Paper” 3D Interdigital Microelectrodes for High Performance Metal‐Free Flexible Supercapacitors

Flexible micro-supercapacitors (MSCs) are promising power sources of portable/wearable electronic devices. Electrodes are the key components determining performance of the MSCs, but it still remains a big challenge in either materials or fabrication methods to achieve both high charge storage capability and robust mechanical flexibility. Herein, a novel water-cooling assisted selective laser ablation (WASLA) technique is demonstrated for scale-fabrication of "embedded-in-paper" 3D graphene-cellulose composite interdigital electrodes (3D GCCIEs) in a mask-free and chemical-free manner. The obtained electrodes are endowed with 3D charge storage geometry, high electrical conduction, freely designed patterns, and the inherent advantages of paper substrate. Therefore, the 3D GCCIEs-based MSC exhibits excellent overall performance including large specific capacitances, high rate performance, impressive cyclic stability, and remarkable mechanical flexibility. Moreover, metal-free 3D GCCIE-MSC integrated arrays with diverse shapes composed of linear/curved interdigital electrodes are also fabricated, and a letter-shaped MSC array successfully lit a light emitting diode light in both flat and folded status demonstrating excellent device flexibility. The as-fabricated 3D GCCIE-MSCs have shown great application potential as power sources of flexible electronic devices, and the WASLA method proves to be an effective strategy for scale-manufacturing high performance paper-based charge storage devices not limited to supercapacitors.